An air-breathing valveless PDE model was designed and manufactured, which was made up of subsonic inlet, mixing chamber, ignition chamber, detonation chamber. The total pressure recovery coefficient, flux coefficient and intake resistance with six different induction systems were measured by a semi free subsonic flow field. The proof-of-principle experiments of PDE model with different induction systems were all successfully carried out, by using liquid gasoline-air mixture with low-energy system (total stored energy less than 50 mJ). The measured detonation wave pressure ratio was very close to that of C-J detonation. The air-breathing PDE model was easy to initiate and worked in good condition. The deflagration to detonation transition (DDT) and operation frequency effect on pressure traces were also investigated by experiments. The results indicated the oscillation of pressure peak at P6 enhanced with the operation frequency increased. DDT accomplished before P6 and the DDT distance was about 0.9 m (from the ignitor).

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This paper focused on the mixer optimization by numerical simulation. The mixing and flow characteristics inside two different lobed mixers with/without centrum were obtained by 3-D CFD simulation. The core flow was the hot rich-methane/O 2 (1)burnt gas, while the cold air flew by the by-pass. The air/burnt gas flow ratio was improved from 7 to 9 in order to confirm the effect of air/burnt gas ratio on the mixing and flow characteristics. The simulation results indicated that no matter which mixer was used, there were a pair of symmetrical re-circulation regions in the mixers, and the total temperature and species distribution turned to be more uniform at the increased mixing length. The mixing performance in the lobed mixer with centrum was slightly better than that of the lobed mixer without centrum, and the length of re-circulation region in the lobed mixer with centrum was slightly shorter than that of the lobed mixer without centrum. The air/burnt gas ratio had considerable effect on the mixing and flow characteristics. The mixing performance with air/burnt gas ratio of 9 was much better than that of air/burnt gas ratio 7. Similar mixing performance would attain in the case of air/burnt gas ratio 9 with only half of the mixing length in the case of air/burnt gas ratio 7. The re-circulation region in the case of air/burnt gas ratio 9 occurred ahead of that of air/burnt gas ratio 7, and the former was longer than the latter.